Bearingless motor system design for industrial applications

This paper considers the development of a practical, low cost bearingless motor system for use in large industrial applications. Bearingless motor technology is proposed as an ultra efficient, highly integrated solution in fluid handling systems which currently use high speed (over 7 kRPM) centrifugal blowers/pumps. Over 40 potential industrial users have been interviewed to identify their needs and the shortcomings of current commercial solutions, with an emphasis placed on wastewater treatment. Based on these interviews, a motor topology is selected, a novel bearingless motor is designed, and 3D finite element analysis (FEA) is used to investigate the design space and tradeoffs. Mechanical design constraints on the high speed rotor geometry are considered as well as a detailed magnetic design for a 30 kRPM, 100kW system. Preliminary analysis indicates an efficiency of 96.5 percent. The resulting design is a highly novel 4-pole bearingless ac homoplar motor utilizing a Dual Purpose No Voltage (DPNV) Winding, which to the authors' knowledge has not previously been investigated in this configuration.